During tanning production processes, large quantities of waste liquids and waste solids are produced, which contain plentiful lime, salts, oil and grease, ammonia and other nitrogen compounds, proteins, sulfides, chromates, dyes, hairs, leather residues, silts, and other waste products. The wastes have very high chemical oxygen demand (COD) and biochemical oxygen demand (BOD), high variation coefficients and a stench. These industrial wastes are difficult to treat and generate serious contamination to the environment.
As society is setting higher standards for environmental protection, how to treat tanning waste liquids has become a difficult issue that must be addressed by the industry. To solve this difficult problem, through many years of research and development, and commercial applications, it has been found that the waste liquids are actually valuable and can be reused since they contain a lot of beneficial ingredients. Making leather with waste liquids can produce leather with quality superior to those made from conventional processes that use fresh water. Enzymes and decomposition products in the waste liquids are all beneficial for leather production. For example, amino acids and saponified substances are beneficial for filling collagen fibers and enable the waste liquids to maintain a stable state. The present process takes advantage of the beneficial properties of waste liquids to produce leather using waste liquids. The present process effectively solves environmental protection issues for the tanning industry, and improves product quality. This new process provides the tanning industry with both economic and environmental benefits.
In the tanning industry, the terms “hide” and “skin” are oftentimes used interchangeably, each referring to the integument or natural covering of an animal. Since the term “hide” is most often associated with larger animals such as cows or bison, the term “hide” will be used hereinafter. It should be understood, however, that the process for the production of leather described and claimed herein can be applied equivalently to animal skin as well as animal hide.